Getter assembly



Oct. 12, 1965 P. V. MALLOY GETTER ASSEMBLY Filed June 21, 1962 iili.

INVENTOR PAUL V.MALLOY BY J) A 7 ATToRNfi United States Patent w 3,211,280 GETTER ASSEMBLY Paul V. Malloy, Lakewood, Ohio, assignor to Union Carbide Corporation, a corporation of New York Filed June 21, 1962, Ser. No. 204,264 6 Claims. (Cl. 206-.4)

The invention relates to a getter construction which is free from harmful loose particles of getter material, and includes a method for making same.

High vacua are commonly produced in radio tubes and other vacuum apparatus by pumping most of the gas out of a tube envelope and subsequently increasing the vacuum thus obtained by vaporizing or flashing within the envelope a highly reactive substance or getter material" which adsorbs or reacts with residual gases. Usually, this material principally comprises a comminuted mixture or alloy of active metals such as barium, magnesium, and aluminum.

The getter construction for insertion in a vacuum tube frequently consists of a holder or getter tab with a tablet of the getter material attached thereto by pressing or by embedding the tablet in the holder. Another construction frequently used consists of a container, such as an annular U-shaped receptacle, with the getter material stamped into the container. In both of these constructions, there is a marked tendency for small particles of getter material to be loosely bound to the main body of getter material. These particles usually exist at the junction between the holder or container and the main body of getter material.

Upon flashing, these particles are oftentimes violently expelled from the getter construction as molten particles, not as gaseous molecules. If these expelled molten particles strike the tube envelope, and if the envelope is made of glass as it frequently is, the impact between the molten particles and the relatively cold glass often causes the latter to crack. Even if the molten particles do not crack the envelope, the loose metallic particles remaining within the envelope interfere with proper tube performance, especially during acceleration and deceleration.

The principal object of the invention, therefore, is to provide a construction of a getter assembly which is substantially free from loose particles of getter material.

Another object is to provide a method for making an improved getter assembly substantially free from loose particles of getter material.

In the drawing:

FIG. 1 is a cross-sectional view of a getter assembly made in accordance with the invention;

FIG. 2 is a cross-sectional view of the components of a getter assembly in place in a die with a punch overhead before the getter assembly of the invention is made; and

FIG. 3 is a cross-sectional view of the getter assembly of the invention in place in a die with a punch at the end of its downward stroke.

Broadly, the above objects are achieved by making a getter assembly which comprises a hollow container filled with getter material, the top surface of each wall of the container and the top surface of adjacent getter material forming a smooth, continuous surface. Such a construction eliminates the existence of loose particles at the junction of the container walls and the getter material. The method of the invention by which the above construction is made comprises providing a hollow container, dispensing the getter material into the container, and stamping the filled container with a punch having a width substantially equal to the width of the container, including its walls.

The invention will be better understood by referring to FIG. 1, which shows a cross-sectional view of a getter assembly made in accordance with the invention. The

3,211,280 Patented Oct. 12, 1965 getter assembly there shown consists of an annular U- shaped receptacle 10 filled with a getter material 12. The getter material 12 may be composed 'of any active material which is suitable for adsorbing or reacting with residual gases in a vacuum device, but the material 12 preferably comprises about 40 percent to 60 percent by weight barium and about 60 percent to 40 percent by weight aluminum in the form of an alloy.

As shown in FIG. 1, the top area 14 consisting of the tops of the container walls 16 plus the exposed area of the getter material 12 is a smooth, V-shaped concave surface free from loose particles of getter material, and the top of each wall 16 plus the adjacent area of the getter material 12 forms a smooth, continuous surface over each junction of the getter material 12 with the walls 16. The top area of the prior art constructions was discontinuous at the junction of the container walls and the getter material, and loosely bound particles almost always existed at this place of discontinuity.

Referring now to FIG. 2, which is partial cross-sectional view, the ordinary components of a getter assembly are shown in place in a die before a getter assembly is made by the method of the invention. The container 18 is disposed in a die 24 suitably made of tungsten carbide. The container 18 is an ordinary annular U-shaped receptacle having two walls 20 and 22, the top surfaces of which are perpendicular to the rise of the walls, and the container 18 is suitably composed of iron coated with about 0.006 inch of nickel, or stainless steel preferably containing about 18 Weight percent chromium and about 11 Weight percent nickel. Thus the container 18 can be made of iron or steel.

A particulate getter material 26 having a suitable particle size, such as about 200 to 350 U.S. mesh, is dispensed into the container 18 until the container 18 is filled to about its top edge or above. Those skilled in the art will realize that the preferred height of the getter material 26 is dependent upon several factors such as grain size of the getter material, the distance across the container walls, the depth of the getter material in the container, and the extent of compacting desired. It will be apparent that the preferred height can be easily determined at the time the getter assemblies are made.

Next, the container 18 filled with getter material 26 is stamped with a punch 28 having a width or thickness greater than the width of the getter material and substantially equal to the distance across the top surface of the container walls 20 and 22 plus the exposed area of the getter material 26. As shown in FIG. 3, the punch 28 compresses on its downward stroke both the top surfaces of the container walls 20 and 22 and the top surface of the getter material 26 to form a smooth, V shaped concave surface consisting of the top surface of each wall and the top surface of adjacent getter material.

The punch 28 is preferably beveled to form a crosssectional V, but it may be arcuate in shape or flat, although a flat punch is the least preferred of the three shapes. It will be apparent that the main consideration for the shape of the punch 28 is that it form a smooth, continuous surface across the junction of a container wall and the getter material. Preferably, the width or thickness of the punch 28 is as large as possible without causing interference between the punch and the die walls as the punch descends.

Tests of the getter assembly of the invention indicate the following characteristics:

(1) The getter assembly is particle-free because no unpressed area of getter material exists.

(2) Due to a lack of loose particles, a smaller area of getter material isexposed to the atmosphere, thereby minimizing undesirable reactions of the getter material with the atmosphere or with water.

(3) The getter assembly exhibits a progressive flash because of the relatively thin mass of getter material near the junction of the getter material and a container wall.

(4) The container walls are of equal height with minimum distortion and the container walls direct vaporized getter material in a certain path since the main body of getter material usually lies below the top edges of the container walls.

(5) A stronger, wider punch can be used in the production of the getter assemblies, thereby reducing the amountof punch breakage.

It is manifest that the getter assembly of the invention possesses many desirable characteristics which prior art constructions do not have.

What is claimed is:

1. A particle-free getter assembly comprising a hollow container and a getter material filling said container, the top surface of each wall of said container and the top surface of adjacent getter material forming a smooth, continuous surface.

2. The getter assembly defined in claim 1 wherein said container is a channeled ring container.

3. The getter assembly defined in claim 1 wherein said container is made of a material selected from the group consisting of iron and steel.

4. The getter assembly defined in claim 1 wherein said getter material comprises by weight to barium and 60% to 40% aluminum.

5. A particle-free getter assembly comprising a channeled ring container and a getter material filling said container, the top surfaces of the inner and outer walls of said container and the top surface of said getter material forming a smooth V-shaped concave surface.

6. A particle-free getter assembly comprising a channeled ring container and a getter material filling said container, the top surfaces of the inner and outer walls of said container and the top surface of said getter material forming a smooth, continuous concave arcuate surface.

References Cited by the Examiner UNITED STATES PATENTS 2,824,640 2/58 della Porta 2060.4 2,907,451 10/59 della Porta 2060.4 2,943,357 7/60 MacMaster et al. 1855 2,994,109 8/61 Thomas 1855 3,023,883 3/62 Meisen 2060.4 3,033,354 5/62 della Porta 206--0.4

THERON E. CONDON, Primary Examiner.

EARLE J. DRUMMOND, GEORGE O. RALSTON,

Examiners. 

5. A PARTICLE-FREE GETTER ASSEMBLY COMPRISING A CHANNELED RING CONTAINER AND A GETTER MATERIAL FILLING SAID CONTAINER, THE TOP SURFACES OF THE INNER AND OUTER WALLS OF SAID CONTAINER AND THE TOP SURFACE OF SAID GETTER MATERIAL FORMING A SMOOTH V-SHAPED CONCAVE SURFACE. 